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// Copyright 2015 Google Inc. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package com.google.devtools.build.lib.profiler.chart;
import com.google.devtools.build.lib.profiler.ProfileInfo.Task;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
/**
* Data container to aggregate execution time statistics of multiple tasks grouped by some name.
*/
class TasksStatistics {
public final String name;
public final int count;
public final long minNanos;
public final long maxNanos;
public final double meanNanos;
public final double medianNanos;
/** Standard deviation of the execution time in milliseconds since computation in nanoseconds can
* overflow.
*/
public final double standardDeviationMillis;
public final long totalNanos;
public TasksStatistics(
String name,
int count,
long min,
long max,
double mean,
double median,
double standardDeviation,
long total) {
this.name = name;
this.count = count;
this.minNanos = min;
this.maxNanos = max;
this.meanNanos = mean;
this.medianNanos = median;
this.standardDeviationMillis = standardDeviation;
this.totalNanos = total;
}
public double minimumMillis() {
return toMilliSeconds(minNanos);
}
public double maximumMillis() {
return toMilliSeconds(maxNanos);
}
public double meanMillis() {
return toMilliSeconds(meanNanos);
}
public double medianMillis() {
return toMilliSeconds(medianNanos);
}
public double totalMillis() {
return toMilliSeconds(totalNanos);
}
/**
* @param name
* @param tasks
* @return The set of statistics grouped in this class, computed from a list of {@link Task}s.
*/
public static TasksStatistics create(String name, List<Task> tasks) {
Collections.sort(
tasks,
new Comparator<Task>() {
@Override
public int compare(Task o1, Task o2) {
return Long.compare(o1.duration, o2.duration);
}
});
int count = tasks.size();
long min = tasks.get(0).duration;
long max = tasks.get(count - 1).duration;
int midIndex = count / 2;
double median =
tasks.size() % 2 == 0
? (tasks.get(midIndex).duration + tasks.get(midIndex - 1).duration) / 2.0
: tasks.get(midIndex).duration;
// Compute standard deviation with a shift to avoid catastrophic cancellation
// and also do it in milliseconds, as in nanoseconds it overflows
long sum = 0L;
double sumOfSquaredShiftedMillis = 0L;
final long shift = min;
for (Task task : tasks) {
sum += task.duration;
double taskDurationShiftMillis = toMilliSeconds(task.duration - shift);
sumOfSquaredShiftedMillis += taskDurationShiftMillis * taskDurationShiftMillis;
}
double sumShiftedMillis = toMilliSeconds(sum - count * shift);
double mean = (double) sum / count;
double standardDeviation =
Math.sqrt(
(sumOfSquaredShiftedMillis - (sumShiftedMillis * sumShiftedMillis) / count) / count);
return new TasksStatistics(name, count, min, max, mean, median, standardDeviation, sum);
}
static double toMilliSeconds(double nanoseconds) {
return nanoseconds / 1000000.0;
}
}
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